This invention relates generally to repair methods for internal combustion engines. More particularly, this invention relates to equipment and methods for installing and removing a camshaft or other engine components without removal of the cylinder head.
In the course of engine repair and maintenance, defective or obsolete engine components are removed and replaced with new or similar engine components. The repair process typically requires the removal and subsequent reinstallation of other auxiliary or associated engine components due to limited space in the engine compartment of a vehicle. The repair process is many times time consuming, cumbersome, difficult and oftentimes expensive.
For example, the repair or replacement of an engine camshaft or rear half of a front cover typically requires the removal of the cylinder head and cylinder head gasket along with other engine components. Existing repair methods for replacing a camshaft require the removal of the cylinder head, and attached gasket, to gain access to the roller tappets which sit on the camshaft lobes. The roller tappets are then removed which allow removal of the camshaft. Further, not only must the cylinder head and cylinder head gasket be removed but a new cylinder head gasket must be used when reinstalling the cylinder head on the engine case or block. This is the case, since the cylinder head gasket is always damaged in removal process. Moreover, existing methods of repairing or replacing a camshaft or a rear half of the front cover, including removal and reinstallation of the cylinder head and new gasket, are time consuming (e.g., a typical time is on the order of 1.5 man-hours) which leads to higher repair costs.
Accordingly, there is a need for more efficient and cost effective method that does not require the removal of the cylinder head or cylinder head gasket, for the removal or replacement of internal combustion engine components, such a camshaft or a rear half of a front cover.
The present invention provides a method for suspending roller tappets (also know as cam followers or valve lifters) in an internal combustion engine without removing the cylinder head and cylinder head gasket. The suspension of the roller tappets in the engine allow for the simplified removal and replacement of front engine components such as a camshaft or the rear half of a front cover among others. The method of the present invention comprises the steps of removing the rocker arm assembly or assemblies on the engine. Next, each push rod is removed and replaced with a corresponding tappet suspension tool to thereby engage a top portion of corresponding roller tappet. A suspension tool guide bar is then installed such that the plurality of tappet suspension tools are connected and can then be simultaneously moved in unison. All roller tappets are then moved to or suspended in a raised position above the camshaft, via movement of the suspension tool guide bar, thereby forming a clearance between the roller tappets and camshaft bearings. Next, the roller tappets are secured in the raised position by installing securing blocks between the suspension tool guide bar and the engine case. This method can be used for removal of a camshaft or the front half of a front cover.
In an embodiment of the present invention, the method can be used to replace the camshaft in an engine without removing the cylinder head and cylinder head gasket. This method uses the steps just described plus the additional the step of removing the camshaft from the engine block. The replacement camshaft can be installed by following the steps in reverse order.
In another embodiment of the present invention, the method can be used to replace the rear half of a front cover, without removing the cylinder head and cylinder head gasket. This method uses the steps just described plus the additionalsteps of removing the idler gears, removing the camshaft from the engine case, and finally removing the rear half of the front cover from the engine case. A rear half front cover can then be installed by following the steps in reverse order.
The following drawings and description set forth additional advantages and benefits of the invention. Other advantages and benefits will be obvious from the description and may be learned by practice of the invention.